Activating the Flash Player is not working anymore since Tor Browser 5.0.5

There are a bunch of users that are complaining about the Flash Player not working anymore e.g. on sites like www.pandora.com. What is going on, I think, is the detection being broken which is very likely due to the fix for legacy/trac#17207 (moved). The Flash Player itself is still working for me, e.g. on Adobe's test site.

It's unfortunate that this did not get caught in our alpha series but here we are. I guess providing a preference allowing to disable the fix for legacy/trac#17207 (moved) might be worth it given that a number of users wouldn't be using Tor Browser otherwise or would be trying to shoot themselves in the foot with having different browsers opened simultaneously.